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<p>This study presents a comprehensive microstructural failure analysis of copper-strand-embedded carbon fiber/epoxy (CFRP) composite laminates, complemented by a hybrid genetic algorithm–differential evolution (GA–DE) optimizer aimed at maximizing fracture energy within void content constraints. Three design parameters were optimized: fiber volume fraction Vf (0.30–0.60), resin–hardener ratio <i>R</i> (6:1–11:1), and stacking sequence <i>S</i> ([0/90/0]s, [0/45/90]s, [0/0/90]s). An experimental matrix comprising 45 specimens was characterized through short-beam interlaminar shear testing (ASTM D 2344), double-cantilever beam Mode I fracture toughness testing (ASTM D 5528), and systematic SEM fractography. Quantitative failure-mode mapping identified fiber pullout (38%), matrix cracking (27%), interfacial debonding (20%), fiber fracture (10%), and delamination (5%) as the hierarchical damage sequence. Weibull analysis of tensile data yielded parameters <i>m</i> = 12.4 and characteristic strength <i>σ</i><sub>0</sub> = 308&#xa0;MPa, with a B-basis design allowable of 268&#xa0;MPa, representing a 14% increase above the minimum secondary-structure requirement of 235&#xa0;MPa. Interlaminar shear strength (ILSS) peaked at 38.4 ± 1.8&#xa0;MPa for the resin ratio of 8:1. The GA–DE optimizer identified Vf = 0.52, <i>R</i> = 8:1, and [0/90/0]s stacking sequence as the global optimum, predicting a fracture energy G<i>Ic</i> of 2.42&#xa0;kJ/m<sup>2</sup>, which exceeds the baseline value of 2.18&#xa0;kJ/m<sup>2</sup> by 11%. The hybrid approach outperformed the differential evolution-only and genetic algorithm-only methods by 0.14&#xa0;kJ/m<sup>2</sup> and 0.11&#xa0;kJ/m<sup>2</sup> (6.1% and 4.8%), respectively, at a total budget of 120 iterations. Mode I R-curve DCB analysis confirmed an initiation G<i>Ic</i> of 0.41&#xa0;kJ/m<sup>2</sup> and a propagation plateau at 0.61&#xa0;kJ/m<sup>2</sup> for the optimized configuration. Fatigue S–N analysis indicates a 6% improvement in the endurance limit for the optimized configuration relative to the baseline. A multi-objective Pareto front delineating fracture energy versus void content provides valuable quantitative guidance for damage-tolerant CFRP fabrication.</p>

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Microstructural Failure Analysis and Hybrid GA–Differential Evolution Optimization of Fracture Energy in Copper-Embedded Carbon Fiber/Epoxy Composites

  • 期刊论文

  • 发表日期：

    2026年7月29日

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  • M. Jasmine Sabeeka,
  • Ajith Raj Rajendran,
  • Muhammed Anaz Khan

摘要

This study presents a comprehensive microstructural failure analysis of copper-strand-embedded carbon fiber/epoxy (CFRP) composite laminates, complemented by a hybrid genetic algorithm–differential evolution (GA–DE) optimizer aimed at maximizing fracture energy within void content constraints. Three design parameters were optimized: fiber volume fraction Vf (0.30–0.60), resin–hardener ratio R (6:1–11:1), and stacking sequence S ([0/90/0]s, [0/45/90]s, [0/0/90]s). An experimental matrix comprising 45 specimens was characterized through short-beam interlaminar shear testing (ASTM D 2344), double-cantilever beam Mode I fracture toughness testing (ASTM D 5528), and systematic SEM fractography. Quantitative failure-mode mapping identified fiber pullout (38%), matrix cracking (27%), interfacial debonding (20%), fiber fracture (10%), and delamination (5%) as the hierarchical damage sequence. Weibull analysis of tensile data yielded parameters m = 12.4 and characteristic strength σ0 = 308 MPa, with a B-basis design allowable of 268 MPa, representing a 14% increase above the minimum secondary-structure requirement of 235 MPa. Interlaminar shear strength (ILSS) peaked at 38.4 ± 1.8 MPa for the resin ratio of 8:1. The GA–DE optimizer identified Vf = 0.52, R = 8:1, and [0/90/0]s stacking sequence as the global optimum, predicting a fracture energy GIc of 2.42 kJ/m2, which exceeds the baseline value of 2.18 kJ/m2 by 11%. The hybrid approach outperformed the differential evolution-only and genetic algorithm-only methods by 0.14 kJ/m2 and 0.11 kJ/m2 (6.1% and 4.8%), respectively, at a total budget of 120 iterations. Mode I R-curve DCB analysis confirmed an initiation GIc of 0.41 kJ/m2 and a propagation plateau at 0.61 kJ/m2 for the optimized configuration. Fatigue S–N analysis indicates a 6% improvement in the endurance limit for the optimized configuration relative to the baseline. A multi-objective Pareto front delineating fracture energy versus void content provides valuable quantitative guidance for damage-tolerant CFRP fabrication.